Sorting good germs from bad in the bacterial world

December 2, 2013

Arizona State University scientists have developed a microfluidic chip that can sort good germs from bad.

Your intestines are home to about 100 trillion bacteria. That’s more than the number of cells that comprise the entire human body. Armies of bacteria sneak into our bodies the moment we are born – uninvited, but necessary guests. E. coli and bacteria populations isolated on a microdevice Download Full Image

For the most part, these bacteria are industrious and friendly. Some of them are even beneficial, helping with digestion and producing vitamins. A few miscreants, though, will kill us if we let them stay.

Sometimes the difference between harmless and harmful is miniscule. Take E. coli, for instance. Billions of E. coli organisms live in the average person’s intestines. They go about their business causing no trouble whatsoever. However, one particular strain of E. coli, O157:H7, causes about 2,000 hospitalizations and 60 deaths in the United States every year. The differences between this strain and others are detectable only at the molecular level.

But how do we separate friend from foe? Determining whether or not bacteria are harmful usually requires growing cultures from food or infected patients. This is a time-consuming process that must be carried out in a laboratory. Since an estimated 9.4 million cases of food-borne illness occur each year in this country, we stand to gain much from new technologies that can rapidly identify microorganisms.

Scientists at ASU's Department of Chemistry and Biochemistry, within the College of Liberal Arts and Sciences, have developed a new device that could significantly speed up the identification process for harmful bacteria and other microorganisms. The team, led by professor Mark A. Hayes, hopes to create handheld, battery-operated devices that could deliver answers in minutes, instead of days.

Identification takes place within a microscopically small channel in a chip made from glass or silicone polymer. The microchannel features saw-tooth shapes that allow researchers to sort and concentrate microbes based on their unique electrical properties.

The phenomenon that makes this work is called dielectrophoresis, which involves an applied voltage that exerts force upon the bacteria. This force acts like a coin-sorter, causing bacteria to become trapped at different points along the channel. Where they stop, and at what voltage, depends on their molecular and electrical properties.

Using this approach, Hayes’s team, including graduate student Paul V. Jones, has separated extremely similar bacteria – pathogenic and nonpathogenic strains within the single species, E. coli. Their results have recently been published in “Online First,” on SpringerLink and in the journal Analytical and Bioanalytical Chemistry.

“The fact that we can distinguish such similar bacteria has significant implications for doctors and health officials,” says Hayes. "E. coli O157:H7 is very similar in size and shape to other subtypes of the bacteria. But unlike many of the others it has the ability to produce shiga-like toxin, a protein that breaks down blood vessel walls in the digestive tract.”

Fortunately, all of these bacterial strains also possess subtle, but telltale differences in the proteins and other molecules that they express on their surface. According to Hayes, dielectrophoresis is well-suited to probe these phenotypic differences.

The researchers used an ordinary strain of E. coli along with two pathogenic varieties. They injected the cells into each channel and simply applied voltage to drive the cells downstream. The geometric features of the channel shape the electric field, creating regions of different intensity. This field creates the dielectrophoretic force that allows some cells to pass, while trapping others based on their phenotype.

So far, the device has only been used to test pure cultures of bacteria, but they hope soon to test complex mixtures of particles that are found in nature or the human body.

The next step is to create cheap, portable devices that would enable point-of-care or field-based analysis. Such a device would require no time-consuming culturing or other tests, which would allow rapid response to disease or contamination, hopefully saving lives.

This work was supported by the NIH National Institute of Allergy and Infectious Diseases (grant number: 5R03AI099740-02).

Jenny Green

Clinical associate professor, School of Molecular Sciences


New program provides grants to nonprofits to fight hunger, conflict and poverty

December 3, 2013

Buffett Foundation, ASU partner on 40 Chances Seed Grants Program

In recognition of #GivingTuesday, the Howard G. Buffett Foundation today announced a new program to engage young people in identifying innovative and impactful efforts to address hunger, conflict and poverty. In partnership with ASU’s Lodestar Center for Philanthropy & Nonprofit Innovation, the Buffett Foundation will solicit proposals through the 40 Chances Seed Grants program. Download Full Image

The new program will provide 40 grants, each worth $10,000, to the most innovative nonprofit organizations using strategies built on the effective philanthropic principles described in the New York Times best-selling book "40 Chances: Finding Hope in a Hungry World," written by Howard G. Buffett with Howard W. Buffett.

“Giving Tuesday is the perfect occasion for us to make this major announcement,” said Howard G. Buffett, chairman and CEO of the Howard G. Buffett Foundation. “Everywhere I go in the United States, people ask me how they can help improve our world if they don’t have significant financial resources. I am a firm believer that to address hunger and poverty globally, we need everyone to play a role. Through the 40 Chances Seed Grants program, we can recognize, strengthen and support organizations doing great work.”

“ASU is proud to join with the Buffett Foundation in support of this transformational program, which aligns closely with our institutional commitment to foster innovative solutions that yield real world change,” said ASU President Michael M. Crow. “Our students and faculty are excellent ambassadors eager to advance the recognition and success of our nation’s nonprofits.”

Through the partnership, students and faculty at Arizona State University will identify the organizations with the highest potential for impact and the Howard G. Buffett Foundation will make the final determinations on all grant recipients. 

“We are excited to be a part of this truly innovative program to support the Buffett Foundation’s mission to help the world’s most vulnerable populations,” said professor Robert F. Ashcraft, executive director of the Lodestar Center for Philanthropy & Nonprofit Innovation in ASU's College of Public Programs and its School of Community Resources and Development.

“By identifying and providing funding support to new ideas the foundation might not see otherwise, it creates a unique ability to seek solutions from truly anywhere around the world," Ashcraft said. "By engaging our students and faculty in the selection process through this philanthropic learning laboratory, they will earn credit as part of a unique class experience. As a result, we are also paving new ground in terms of educational partnerships between academic institutions and private philanthropy.”

“We have learned over the last decade that you have to take risks to create change,” said Howard G. Buffett. “We have also learned that the best ideas come from people who are on the ground, working every day to solve problems.”

Seed grants will be awarded twice per year, and winners for the first round of grants will be announced in the spring of 2014. Organizations must have U.S. 501(c)(3) tax-exempt status or be sponsored by an organization with U.S. 501(c)(3) tax-exempt status to be eligible for consideration. Forty grants will be awarded over four years, for a total of $400,000. Recipients of seed grants will be expected to provide a report on the grant’s impact following the implementation of funds.

#GivingTuesday was created to designate the Tuesday following Thanksgiving, Black Friday and Cyber Monday as a national day of giving.

Find out more information about the 40 Chances Seed Grants program by visiting

Sharon Keeler